Ontogenetic studies of seizure patterns and seizure activities induced by cortical focus

Ontogenetic studies of epileptogenic process were carried out in albino rats ranging in age from birth to 45 days. Experimental epilepsy was produced by two different procedures and the results were compared with each other. Tungstic acid gel was applied to the motor area of the left side of the cortex, and the following results were obtained. The latency of the seizure appearance was long during 10 days after birth, became progressively short thereafter and reached the minimum in about 20 days of age, and gradually returned to the adult level again by 45 days of age. No abvvious seizure was exhibited until five days of age. Seizure patterns developed from tonic or twitch-like jerky convulsion (10 days old) to rhythmic or clonic type of seizure (13 days old), and the seizure patterns similar to those in the adult rat were observed in about 20 days of age. Cortical seizure activity was initially observed in about 10-day-old rats; single high amplitude slow wave appeared and small spikes became superimposed on it in the course of maturation. Atypical spike and wave complexes were observed after 20 days of age. Electrical stimulation was applied to the left cortical motor area by constant current stimulator, and the following seizure patterns were observed: No obvious seizure could be elicited in newborn rat, whereas from three days of age, tonic seizure of the whole body, and from seven days old twitch-like convulsion of extremities were observed. In ages from 10 to 20 days, seizure induced by electrical stimulation was mainly tonic in pattern; extension of forelimbs and flexion of hindlimbs in most cases were observed before 13 days old, but both fore-and hindlimbs were extended therafter. Tonic-clonic seizure patterns were exhibited after 20 days of age. From these results, it was considered that tonic convulsions and high voltage slow cortical seizure activites were produced from the activites of the local cortical neuronal connections, and rhythmic and/or clonic seizure patterns and spike and wave seizure activities were elicited from the more complex, i.e. cortico-subcortical neuronal circuits. Possible contributing factors for the determination of seizure susceptibility in immautre rats were also discussed.